A musical not played on one instrument can be easily distinguished from the same note played on another. The teo notes are said to differ in quality or timbre. Generally speaking, a musical note does not consist of sound of a different frequency – it is a subtle blend of frequencies, the blend in question being distinctive to each instrument. The strongest audible frequency is called the fundamental and gives the note its characteristic pitch. The accompanying frequencies are called overtones and determine the quality of the note.
The notes of a trumpet contain strong overtones of high frequencies, while notes produced by an organ are mellower. Practically all the sound energy of notes produced by an organ is is concentrated in the fundamental frequency. The overtones are fewer and lower in intensity. The diagram below shows typical notes from a few instruments.
Much experience and craftsmanship is used to make instruments that produce notes of the desired quality. Undesired overtones must be suppressed and desirable overtones emphasised.